The embodiment relates to an apparatus and a method for controlling an input signal, which can exactly measure a signal input to a PLC (Programmable Logic Controller).
Automatic equipment used in industrial fields consists of mechanical equipment including a relay. There is a difficulty to change the automatic equipment consisting of the mechanical equipment because internal circuits of the automatic equipment must be changed. In order to overcome such a difficulty, the PLC is used.
The PLC includes an analog input module. The analog input module of the PLC may include a circuit for converting an analog input signal into a digital value. The analog input signal may include an analog direct current or an analog direct current voltage.
In order to convert an analog input signal into a digital signal, the analog input module of the PLC may measure a value of the analog input signal after receiving the analog input signal. However, since hardware, such as a resistor or an amplifier (OP-Amp) which constitutes the analog input module, causes an error in an analog input signal value, it is difficult to exactly measure the analog input signal value.
Therefore, after a reference signal is input to the analog input module, the analog input signal may be corrected based on the reference signal in order to exactly measure the analog input signal value. However, since the signal correcting scheme using a linear equation according to the related art measures the analog input signal several times, this scheme requires much time and, when the analog input signal is a nonlinear signal, this scheme cannot be applied.